Data storage systems are arrangements of hardware and software that include one or more storage processors coupled to arrays of non-volatile storage devices. The storage processors service storage requests, arriving from host machines (“hosts”), which specify files or other data elements to be written, read, created, or deleted, for example. Software running on the storage processors manages incoming storage requests and performs various data processing tasks to organize and secure the data elements stored on the non-volatile storage devices.
In order to satisfy different performance needs, a data storage system may include several storage tiers, each storage tier having respective performance characteristics. For example, the data storage system may provide a “Gold” storage tier for applications having very high performance needs, a “Silver” tier for applications having somewhat high performance needs, and a “Bronze” tier for applications having normal performance needs. The “Gold” storage tier may be made up of high speed solid state storage devices, the “Silver” tier may be made up of high speed magnetic drives, and the “Bronze” tier may be made up of standard magnetic drives. Some host-accessible data objects, such as LUNs, file systems, per-VM virtual volumes (VVols), etc. may be drawn from a particular storage tier in the case of use for a particular application having special performance needs. Other storage objects may not have specified storage tiers, being drawn from a variety of available storage tiers.